welcome_stranger,
this excerpt from the J* conditions of carraige should clear up your query:
9. SCHEDULES, LATE OR CANCELLED FLIGHTS
9.1 Schedules
(a) The flight time shown on your Itinerary and Tax Invoice may change between the date of issue and your date of travel. Jetstar does not guarantee the flight times and they do not form part of your contract of carriage with us.
(b) Before we accept your booking, we or our Authorised Agents will tell you the scheduled departure time of your flight and it will be shown on your Itinerary and Tax Invoice. We may need to change the scheduled departure time of your flight after your Itinerary and Tax Invoice has been issued. If you give us or our Authorised Agents contact information, we or they will try to let you know about any changes.
(c) If, after you pay for your Booking, we make a significant change to the scheduled departure time of your flight or the flight is late or cancelled (except where this is due to bad weather):
and you find this change unacceptable; and
we or our Authorised Agents cannot book you on another flight which you are prepared to accept;
we will give you a fare refund.
9.2 Late or cancelled flights (due to bad weather)
Where bad weather is responsible for the delayed or cancelled flight, whether you have checked in or not, Jetstar will try to assist you to get to your destination, but will not be responsible for paying any costs or expenses you may incur as a result of the delay or cancellation.
9.3 No flight connections provided
Jetstar is a low cost 'point-to-point' airline which does not provide flight connections or baggage transfer. It is the Passenger's responsibility when making bookings to allow time for Baggage collection and recheck. We recommend at least 90 minutes between domestic flights, and at least 150 minutes between an international and a domestic flight. While Jetstar will try to carry you and your Baggage in accordance with the date and time of the flights specified, it does not guarantee it will be able to do so. Schedules may change without notice for a range of reasons including but not limited to bad weather, air traffic control delays, strikes, technical disruptions and late inbound aircraft. To the extent permitted by law, Jetstar excludes liability for any costs, expenses, losses or damages incurred by the Passenger as a result of failure to meet a schedule.